Glycosylation of CD4 and Thy-1

The site-specific glycosylation of soluble recombinant variants of human and rat CD4 (sCD4) expressed in Chinese hamster ovary (CHO) cells has been characterized. The presence of identical oligosaccharides at the conserved glycosylation site in domain 3 of rat and human sCD4 and the greater abundance of oligomannose and hybrid type glycans at the non-conserved glycosylation site of rat sCD4 clearly indicate that the protein structure influences oligosaccharide processing. Comparisons of rat sCD4 glycopeptides with mutant molecules with only single glycosylation sites and with a truncated form containing only the two NH2-terminal domains, indicate that independent processing occurs at each glycosylation site and that domain interactions can also affect oligosaccharide processing. These and other analyses of sCD2 expressed in CHO cells and Thy-1 purified from various tissues suggest that the diversity of oligosaccharide structures on a protein is regulated by the location of the glycosylation sites and the nature of the target protein, cell and tissue. The functional significance of this control remains to be determined.